PHASE_3_SPECIALIZED_FEATURES.md

Phase 3 Implementation - Specialized Features

Summary

Successfully implemented Phase 3 "Specialized Features" from the FontLab API roadmap. These provide advanced professional font production capabilities through the MCP server.

New Resources (Read-only)

Anchors

• fontlab://glyph/{name}/anchors - Get anchor points for a specific glyph
  • Returns: name, x, y coordinates for each anchor
  • Used for mark positioning and composite glyph construction

Layers

• fontlab://glyph/{name}/layers - Get layer information for a specific glyph
  • Returns: index, name, visible state, shapes count, advance dimensions
  • Supports multi-layer glyph design

Guides & Zones

• fontlab://font/guides - Get all global guides in the font

  • Returns: position, angle, name for each guide
  • Used for alignment and design consistency

• fontlab://font/zones - Get alignment zones (hint zones) for the font

  • Returns: PostScript blue values and other blues
  • Used for hinting and vertical metrics

Total New Resources: 4

New Tools (Write operations)

Anchor Management (3 tools)

1. add_anchor - Add an anchor point to a glyph

   • Parameters: glyph_name, anchor_name, x, y
   • Validates anchor name doesn't already exist
   • Essential for mark-to-base and mark-to-mark positioning

2. remove_anchor - Remove an anchor from a glyph

   • Parameters: glyph_name, anchor_name
   • Removes specified anchor by name

3. move_anchor - Move an existing anchor to a new position

   • Parameters: glyph_name, anchor_name, x, y
   • Updates anchor coordinates
   • Returns both old and new positions

Layer Management (2 tools)

4. add_layer - Add a new layer to a glyph

   • Parameters: glyph_name, layer_name
   • Creates new flLayer object
   • Enables multi-layer glyph construction

5. remove_layer - Remove a layer from a glyph by index

   • Parameters: glyph_name, layer_index (0-based)
   • Prevents removal of the only layer
   • Validates layer index range

Guides & Zones (2 tools)

6. add_guide - Add a global guide to the font

   • Parameters: position, angle (optional), name (optional)
   • Uses fontgate fgGuide class
   • Supports horizontal (0°) and vertical (90°) guides

7. add_zone - Add an alignment zone (hint zone) to the font

   • Parameters: zone_type ("blue" or "other_blue"), bottom, top
   • Adds to PostScript hint zones
   • Validates bottom < top

Total New Tools: 7

Bridge Methods Added

Added to fontlab_bridge.py:

• get_glyph_anchors(glyph_name) - Accesses glyph.anchors collection
• get_glyph_layers(glyph_name) - Returns layer metadata with visibility and dimensions
• get_font_guides() - Accesses fg_font.guides via fontgate
• get_alignment_zones() - Returns PostScript blue values from font.info

Implementation Details

Security & Validation

• All glyph names validated for dangerous characters
• Numeric ranges enforced for coordinates and positions
• String length limits for names (255 chars)
• Anchor/layer existence checks
• Zone validation (bottom < top)
• Layer removal protection (cannot remove only layer)

Error Handling

• Comprehensive try/catch in all bridge scripts
• Validation errors logged and returned to user
• Font existence checks
• Glyph/anchor/layer existence checks
• Duplicate prevention for anchors
• Index range validation for layers

FontLab API Usage

• Uses glyph.anchors collection for anchor operations
• Uses flAnchor() class for creating new anchors
• Uses flLayer() and glyph.addLayer() for layer management
• Uses fgGuide() from fontgate for guide creation
• Accesses font.info.postscriptBlueValues and postscriptOtherBlues for zones
• Calls glyph.update() and font.update() for persistence

Coverage Increase

Before Phase 3:

• 20 tools + 13 resources
• ~25% of FontLab API (after Phase 2)

After Phase 3:

• 27 tools + 17 resources
• ~30-35% of FontLab API

Added:

• Complete anchor management system
• Layer creation and removal
• Global guide management
• Alignment zone (hinting) support

Categories Improved:

• Anchors: 0% → 60% (3/5 core tools)
• Layers: 0% → 50% (2/4 tools)
• Guides & Zones: 0% → 50% (2/4 tools)

Use Cases Enabled

1. Mark Positioning & Diacritics

• Add anchors to base glyphs (e.g., "top", "bottom")
• Add anchors to mark glyphs (e.g., "_top" for combining marks)
• Programmatically position marks using anchor coordinates
• Auto-generate mark-to-base and mark-to-mark features

2. Multi-Layer Font Design

• Create color layer fonts
• Manage master layers for interpolation
• Work with construction layers
• Organize glyph variants across layers

3. Design Consistency

• Add horizontal guides for cap height, x-height, baseline
• Add vertical guides for sidebearing consistency
• Use guides for optical alignment
• Programmatic guide management for consistent spacing

4. Hinting & Vertical Metrics

• Define alignment zones for baseline, x-height, cap height
• Set up hint zones for better screen rendering
• Configure PostScript hinting zones
• Maintain consistent vertical metrics across families

5. Automated Font Production

• Batch add anchors to glyph sets
• Programmatic layer management for variable fonts
• Guide-based glyph construction
• Zone setup for font families

Files Modified

1. src/resources.py

   • Added 4 new resource definitions
   • Added URI handlers for anchors, layers, guides, and zones
   • Enhanced URI parsing with proper validation

2. src/fontlab_bridge.py

   • Added 4 new bridge methods with FontLab Python scripts
   • Implemented anchor access via glyph.anchors
   • Implemented layer metadata extraction
   • Implemented guide access via fontgate
   • Implemented zone access via font.info

3. src/tools.py

   • Added 7 new tool definitions with detailed schemas
   • Added 7 new tool handlers
   • Implemented 7 complete tool functions with validation
   • Used flAnchor, flLayer, and fgGuide classes

4. src/utils/validation.py (existing)

   • Used existing validation infrastructure
   • All inputs validated before script execution

API Reference Quick Start

Reading Data

# Get anchors for a glyph
fontlab://glyph/A/anchors
# Returns: {"anchors": [{"name": "top", "x": 300, "y": 700}, ...], "count": 1}

# Get layers for a glyph
fontlab://glyph/A/layers
# Returns: {"layers": [{"index": 0, "name": "Layer", "visible": true, ...}], ...}

# Get all guides
fontlab://font/guides
# Returns: {"guides": [{"position": 700, "angle": 0, "name": "Cap height"}, ...], ...}

# Get alignment zones
fontlab://font/zones
# Returns: {"zones": [{"type": "blue", "bottom": -10, "top": 0}, ...], ...}

Writing Data

# Add anchor
add_anchor(
    glyph_name="A",
    anchor_name="top",
    x=300,
    y=700
)

# Add layer
add_layer(
    glyph_name="A",
    layer_name="Bold Master"
)

# Add guide
add_guide(
    position=700,
    angle=0,  # horizontal
    name="Cap height"
)

# Add alignment zone
add_zone(
    zone_type="blue",
    bottom=-10,
    top=0
)

Testing Notes

To test these features, you'll need:

1. FontLab 7 or 8 installed
2. A font open in FontLab
3. The MCP server running and connected

Test scenarios:

• Anchors: Add "top" anchor to base glyphs, add "_top" to marks
• Layers: Create a new layer for a glyph, remove it
• Guides: Add cap height (700), x-height (500), baseline (0) guides
• Zones: Add blue zone for baseline (-10, 0), add zone for x-height (490, 510)

Next Steps

Remaining in Roadmap:

• Phase 3 (partial): Application Control (workspace, preferences, action sets) - 2 resources + 7 tools
• Phase 4: Automation & Specialty
  • Batch Operations - ~6 tools
  • Color Fonts - 1 resource + 4 tools
  • Hinting - ~3 tools

Future Enhancements:

• Complete anchor tools: auto_anchor, generate_mark_feature
• Complete layer tools: copy_layer, merge_layers
• Complete guide tools: remove_guide, add_stem
• Variable font support (masters, axes, instances)
• Font validation tools
• Import/export enhancements

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Status: ✅ Phase 3 Core Implementation Complete

Total Progress:

• Resources: 17 (was 4 initially)
• Tools: 27 (was 6 initially)
• API Coverage: ~30-35% (was ~10% initially)
• Phases Complete: 1 (Quick Wins), 2 (Professional), 3 (Specialized - core)